The invention relates to a method of manufacturing an electronic device, in particular but not exclusively a semiconductor device, in which method a substrate is placed inside a process chamber and a surface of the substrate is subjected to an ozone treatment.
Ozone gas is suitably applied in a variety of removal applications, such as the removal of organic materials including photoresists and organic contaminants, the removal of metals, salts of metals, particles, and the removal of oxide and regeneration of a controlled chemical oxide. The ozone gas is usually delivered into the process chamber either via an ozonated liquid, which is dispensed onto the surface of the substrate (method A), or via an ozone containing gas whereby an ozone free liquid/vapor is dispensed onto the surface of the substrate (method B). The ozonated liquid, which is a liquid with ozone gas dissolved in it, can be obtained by injection of an oxygen/ozone gas mixture generated by an ozone gas generator into the liquid. In order to specifically target certain contaminants and/or to enhance the effectiveness of the treatment by means of e.g. pH adjustment, the ozonated liquid of method A and the ozone free liquid/vapor of method B are advantageously applied with additives. Such ozone treatment methods as well as mixed forms thereof are disclosed in e.g. WO 99/50898, WO 99/52654, EP 0 959 390, EP 0 548 596.
A disadvantage of method A is that the liquid can not be heated at a high temperature, such as for example 80xc2x0 C., as such a high temperature adversely affects the solubility of the ozone gas and, hence, the ultimate ozone gas concentration inside the process chamber. A high temperature is desired, as it increases the temperature of the substrate and, hence, promotes the reaction kinetics at the surface of the substrate. Moreover, the choice of additives is limited to those additives that are compatible with the ozone gas. For example, ammonium hydroxide can not be comprised in a large concentration without leading to a premature destruction of the ozone gas. Both aspects limit the removal rate at the surface of the substrate.
A disadvantage of method B is that the percentage of ozone gas in the oxygen/ozone gas mixture generated by the ozone gas generator can not be substantially higher than about 10%, which limits the ultimate ozone gas concentration inside the process chamber and, hence, the removal rate at the surface of the substrate. A high ozone gas concentration inside the process chamber is desired, as it promotes the reaction kinetics at the surface of the substrate.
The invention has inter alia for its object to provide a method of the kind mentioned in the opening paragraph, in which method the performance of the ozone treatment is improved.
The ozone treatment of the method in accordance with the invention comprises the steps of:
providing a liquid onto the surface of the substrate via first supply means,
introducing a solution comprising a liquid carrier solvent and ozone gas into the process chamber via second supply means, without bringing about direct contact between the solution and the surface of the substrate.
As the ozone gas is supplied to the process chamber via a separate solution, the temperature of the liquid can be chosen freely without having an adverse effect on the solubility of the ozone gas. Hence, the liquid can now be applied at a high temperature, such as for example 80xc2x0 C., without thereby limiting the concentration of ozone gas that is obtainable inside the process chamber. By using a solution comprising a liquid carrier solvent and ozone gas dissolved in it instead of an oxygen/ozone gas mixture, the percentage of ozone gas can be substantially higher than about 10%. Moreover, as the ozone gas is supplied to the process chamber via a separate solution, the choice of additives is not limited to those additives that are compatible with the ozone gas. For example, ammonium hydroxide can now be comprised in the liquid in a large concentration without leading to a premature destruction of the ozone gas.
In one embodiment of the method in accordance with the invention, the solution comprising the liquid carrier solvent and the ozone gas is dispensed onto a turntable thereby releasing ozone gas, which turntable is separated from the substrate and is used for rotating the substrate. By dispensing the solution onto a moving part of the process chamber instead of a stationary part of the process chamber, the release of ozone gas from the solution is promoted. In this way, a higher ozone gas concentration inside the process chamber can be reached.
Further advantageous embodiments of the method in accordance with the invention are described in the other dependent claims. The invention further relates to an apparatus for subjecting a surface of a substrate, in particular but not exclusively a semiconductor substrate, to an ozone treatment.
Such an apparatus is disclosed in e.g. WO 99/50898, WO 99/52654, EP 0 959 390, EP 0 548 596.
In order to improve the performance of the ozone treatment, the apparatus in accordance with the invention comprises:
a process chamber for accommodating the substrate,
heating means for heating the substrate,
first supply means for providing a liquid onto the surface of the substrate,
second supply means for introducing a solution comprising a liquid carrier solvent and ozone gas into the process chamber without bringing about direct contact between the solution and the surface of the substrate.
Further advantageous embodiments of the apparatus in accordance with the invention are described in the other dependent claims.